{
    "AWSTemplateFormatVersion" : "2010-09-09",

    "Description" : "An example of the AMI Lookup custom resource",

    "Parameters" : {
        "InstanceType" : {
            "Description" : "Example instance types",
            "Type" : "String",
            "Default" : "t1.micro",
            "AllowedValues" : [ "t1.micro","m1.small","m1.medium","m1.large","m1.xlarge","m2.xlarge","m2.2xlarge","m2.4xlarge","m3.xlarge","m3.2xlarge","c1.medium","c1.xlarge","cc1.4xlarge","cc2.8xlarge","cg1.4xlarge"],
            "ConstraintDescription" : "must be a valid EC2 instance type."
        },
        "AmiLookupServiceToken" : {
            "Description" : "ServiceToken of AMI Lookup Custom Resource",
            "Type" : "String",
            "AllowedPattern" : "arn:aws:sns:.*",
            "ConstraintDescription" : "must be an SNS topic ARN"
        }
    },

    "Resources" : {
        "UbuntuInstance" : {
            "Type" : "AWS::EC2::Instance",
            "Properties" : {
                "ImageId" : { "Ref" : "UbuntuAmi"},
                "InstanceType" : { "Ref" : "InstanceType" }
            }
        },
        "WindowsInstance" : {
            "Type" : "AWS::EC2::Instance",
            "Properties" : {
                "ImageId" : { "Ref" : "WindowsAmi"},
                "InstanceType" : { "Ref" : "InstanceType" }
            }
        },
        "UbuntuAmi" : {
            "Type" : "Custom::AmiLookup",
            "Version" : "1.0",
            "Properties" : {
                "ServiceToken" : { "Ref" : "AmiLookupServiceToken" },
                "os": "ubuntu",
                "arch": "64"
            }
        },
        "WindowsAmi" : {
            "Type" : "Custom::AmiLookup",
            "Version" : "1.0",
            "Properties" : {
                "ServiceToken" : { "Ref" : "AmiLookupServiceToken" },
                "os": "windows",
                "arch": "32",
                "version": "Server 2008"
            }
        }
    }
}